WASHINGTON – A bipartisan budget bill that would ease some but not all of painful budget cuts that would otherwise slam the Pentagon and domestic agencies passed a pivotal test in the Senate on Tuesday.

The Senate advanced the measure over a filibuster threshold on a 67-33 vote that ensures the measure will pass the Democratic-led chamber no later than Wednesday and head to the White House to be signed into law.

Top Senate Republicans opposed the bill but didn't try to engineer its defeat. It won sweeping GOP support in the House in a vote last week.

The measure would ease some of the harshest cuts to agency budgets required under automatic spending curbs commonly known as sequestration. It would replace $45 billion in scheduled cuts for the 2014 budget year already underway, lifting agency budgets to a little more than $1 trillion, and it also would essentially freeze spending at those levels for 2015. It substitutes other spending cuts and new fees to replace the automatic cuts and devotes a modest $23 billion to reducing the deficit over the coming decade.

It would also stabilize a broken budget process after a partial government shutdown in October that inflicted political harm upon Republicans. The GOP has since rebounded because of the much-criticized roll-out of Obama's health care law and the party wishes to keep the focus on that topic rather than Washington political brinksmanship.

Twelve Republicans voted with Democrats to advance the measure over a 60-vote filibuster threshold demanded by GOP leaders.

Announcements Monday by Republican Sen. Orrin Hatch of Utah and Georgia Sens. Johnny Isakson and Saxby Chambliss, as well as a strong hint by Sen. John Hoeven, R-N.D., that they would back that step appeared to seal enough GOP support to advance the measure. Sen. Ron Johnson, R-Wis., whose home-state GOP colleague Ryan was a top negotiator on the bill, swung behind it Sunday.

Other Republicans voting for the measure included Roy Blunt of Missouri, Rob Portman of Ohio, Lamar Alexander and Bob Corker of Tennessee, and John McCain and Jeff Flake of Arizona..

"Sometimes the answer has to be yes," Hatch said. "The reality is that Republicans only control one-half of one-third of government. Ultimately, this agreement upholds the principles conservatives stand for and, with Democrats controlling the White House and the Senate, it is the best we could hope for."

Most Senate Republicans opposed the legislation despite the sweeping GOP support it enjoyed in the House last week. But the top Senate Republican, Mitch McConnell of Kentucky, opposed the measure. He is embroiled in a primary with a tea party challenger, businessman Matt Bevin.

In an episode that illustrates the dilemma facing GOP leaders trying to burnish their conservative credentials as they face tea party-backed challengers, the Senate's No. 2 Republican, John Cornyn of Texas, announced his opposition Monday morning on his campaign's website — a step his Senate office was unwilling to take. It was later deleted after reporters from The Associated Press asked for confirmation of a Cornyn quote that appeared on the conservative Internet site Breitbart.com.

"Senator Cornyn opposes this budget deal because it breaks previously set spending caps and goes in the 'wrong direction' with regards to entitlement spending," according to the post. On Monday, his Senate spokeswoman, Kate Martin, would only say that Cornyn would take "a close look" at the measure and is "concerned" that it reverses some of the spending cuts won in a hard-fought 2011 budget pact.

The silence of GOP leaders was taken by Democrats and Republicans alike that McConnell and Cornyn were in the "vote 'no,' hope 'yes'" camp. That's a derogatory term sometime employed by conservative critics who blast Republicans for voting a tea party line when it's clear they actually prefer an opposite result.

"It's a safe bet, pretty safe bet, McConnell will not let this go down," a senior Senate Democrat, Chuck Schumer of New York, said Monday on MSNBC's "Morning Joe." ''I'm sure the Republican leadership, I would bet, is not going to risk another government shutdown. The vote in the House made that certain."

Nobody is claiming the pact worked out between the Ryan and Murray is perfect. It eases $63 billion in scheduled spending cuts over the next two years and replaces them with longer-term savings measured over 10 years, many of which don't accumulate until 2022-23. Deficits would increase by $23.2 billion in 2014 and by $18.2 billion the year after that.

But the deal would put a dysfunctional Washington on track to prevent unappealingly tough cuts to military readiness and weapons, as well as continued cuts to programs cherished by Democrats and Republicans alike, including health research, school aid, FBI salaries and border security. The cuts would be replaced with money from, among other things, higher airline security fees, curbs on the pension benefits of new federal workers or working-age military retirees, and premium increases on companies whose pension plans are insured by the federal government.

But the measure was opposed by groups representing military retirees, who attended a news conference with bill opponents just minutes before the vote.

"We're keeping the government open and screwing all military retirees," said Sen. Lindsey Graham, R-S.C.